Electric cable



Nov. 1938.

F. L.' AIME ELECTRIC CABLE Filed Feb. 14, 1936 BY Md ATTORNEY5 layer of material I between the metal sheath 4 and material 3 so that the copper strips comprising the same may be applied to the insulating wrappings under a considerable tension without cutting or cracking the layers beneath. Material l is preferably made from crumpled paper formed in strips or tapes and wound on the cable in the usual manner The most practical method of soldering the copper strips comprising sheath l is to tin the strips before they are wrapped about the cable in overlapping relationshipI so that the overlapping edges will be united upon the application of heat thereto.

l Since it is only necessary that the barrier layer 3 prevent the migration of the oil during the interval between the application of the barrier material and the soldering of the copper strips to form sheath 4, I have found that a layer of soft unimpregnated paper alone will in many cases delay the penetration of the oil until the operation of soldering has been completed. Such a construction is shown in Fig. 2 in which the layers over the conductor i are respectively oil impregnated paper 2, soft paper 5 and the copper sheath l. As shown in Fig. 2 it is possible to corruzate the outer sheath as at 0 to increase flexibility of the construction. In practice it has been found that the inclusion of a relatively soft layer of material ihas a further advantage in that it becomes possible to smooth the outside of the copper sheath bypassing through an ironing die, all irregularities being taken up by the soft paper layer. The characteristics of the cable structure hereinabove described are further improved where the relatively soi't layer of material 5 which is interposed between metal sheath I and impregnated wrapping I, is comprised of carbon black paper. Carbon black paper when so used performs the dual function of protecting the barrier sheath I and of providing an electrical shield for the cable.

In the above constructionthe insulating layers of paper are hermetically sealed in the enclosing sheath inasmuch as the successive overlapping coils of the strip l are Joined by fusion, soldering or welding.

While a preferred embodiment of the invention has been described and illustrated it is understood that many modifications may be made particularly as to the materials employed without departing from the invention as may be included in the following claim.

What I claim is:

The method of preventing the impregnating composition of insulating wrappings about a cable core from exuding through the overlap portions of an outer metallic spiral sheath while heating the said sheath during soldering said overlap portions together, which comprises enclosing said wrappings and core in a fluid-tight sheath before the application of said outer metallic sheath and thereafter soldering the overlap portions of said metallic sheath while the fluid-tight sheath retains the impregnating composition in the wrapping. 

